4 WORLD GASTROENTEROLOGY NEWS MAY 2017 Editorial | Expert Point of View | WCOG at ACG 2017 | WDHD News | WGO & WGOF News | WGO Global Guidelines | Calendar of Events Defecation occurs through a neurologically mediated series of coordinated muscle movements of the pelvic floor muscles and anal sphinc-ters. Failed relaxation or paradoxical contraction of the puborectalis muscle and external anal sphincter to expel the stool completely leads to impaired rectal evacuation and is termed pelvic floor dyssynergy (PFD). Contribut-ing factors include high anal resting pressures, incomplete relaxation of the pelvic floor and external anal sphinc-ters. Patients often have concomitant slow colonic transit that may improve once the PFD is treated.(2) Etiology The etiology of dyssynergic defeca-tion is unclear. A prospective survey identified the problem beginning in childhood in 31% of patients, and after a particular event like pelvic floor trauma, back injury or pregnancy in 29% of patients, with no cause in 40% of patients.(4) This study also noted that 43% of the patients re-ported frequent passage of hard stools, leading one to believe that straining to expel hard stools may over time lead to dyssynergia. A classic study demon-strated that dyssynergic defecation is a result of the inability to coordinate the abdominal, rectoanal and pelvic floor muscles to facilitate defecation. The failure of rectoanal muscle coordi-nation leads to inadequate propulsive forces, paradoxical contraction of the anal sphincter muscles or inadequate anal relaxation to allow the passage of stool. Approximately half of patients with PFD have also been shown to have impaired rectal sensation which presumably diminishes the urge to defecate.(5) Chronic constipation is associated with impaired quality of life, increased health-care costs and with excess work absenteeism Evaluation Assessment should always start with a comprehensive history focusing on relevant clinical features, including a review of medications. A digital rectal examination and perianal inspec-tion are essential for identifying mass lesions, anal strictures, fissures, and to assess the mechanics of defecation. (6,7) Presence of stool in the rectum is also important to note and a lack of awareness may suggest rectal hyposen-sitivity. During a digital exam, asking patients to “squeeze” will provide information about the anal sphincter muscle tone while “pushing” should elicit relaxation of the external anal sphincter and lead to perineal descent. With the aid of these two maneuvers, dyssynergia can be identified with 75% sensitivity and 87% specificity. Certainly, colon cancer screening is recommended for all patients 50 years or older as well as those with alarm symptoms.(2) Current available tests to assess pelvic floor function include anorectal manometry (ARM) with or without balloon expulsion, standard defecogra-phy, and dynamic magnetic resonance (MR) defecography. Four types of dyssynergic pattern have been identified based on mano-metric findings:(8) • Type I: Abdominal pushing force is adequate, but is associated with a paradoxical increase in anal sphincter pressure. • Type II: Inadequate abdominal pushing force, and a paradoxical anal sphincter contraction. • Type III: Abdominal pushing force is adequate but, either there is ab-sent or incomplete anal sphincter relaxation. • Type IV: Inadequate abdominal pushing and absent or incomplete anal sphincter relaxation. Several studies have found that these patterns were also observed in nearly 90% of asymptomatic controls which is attributed to a non-physio-logic position during the test (left lat-eral position) with an empty rectum. (9) The addition of balloon expulsion adds specificity (80-90%) making it a useful screening test for dyssynergic defecation.(10) Conventional defecography which uses barium paste placed into the rectum provides useful information regarding the presence of anatomic abnormalities that may influence rectal evacuation.(11) However, due to methodological differences and poor inter-observer agreement its role is limited. MR defecography can evalu-ate the anatomy of the pelvic floor and rectal evacuation in dynamic mo-tion. It can provide information about the integrity of the anal sphincters, pelvic floor muscles and the soft tissue surrounding the rectum all without exposure to radiation. There is no single best test and more than one is usually required for accurate diagno-sis. Continued from first page. NOW ONLINE - E-WGN EXPERT POINT OF VIEW ARTICLES COLLECTION! Did you enjoy this expert point of view article? We invite you to check out the entire collection of Scientific and Ex-pert Point of View articles from e-WGN from the past five years on the new WGO website. You can view this article and more at www.worldgastroenterology.org/publications/e-wgn/e-wgn-expert-point-of-view-articles-collection.
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